The present invention relates to an idling operation control apparatus for an internal combustion engine, more particularly to an idling operation control apparatus for an internal combustion engine adapted to regulate the fuel to be supplied to each cylinder so as to minimize dispersion in the output among the cylinders of a multiple cylinder internal combustion engine, whereby a stable idling operation is realized.
In the conventional control system for controlling the amount of fuel injected from a fuel injection pump into a multiple cylinder internal combustion engine, the fuel injection amount for all cylinders is uniformly controlled in common. Accordingly, uniform output cannot be obtained from the cylinders due to differences within the manufacturing tolerance of the internal combustion engine and/or the fuel injection pump and the like.
In particular, non-uniform output of the cylinders causes a conspicuous degradation in the stability of the internal combustion engine during the idling operation of the engine, and this in turn increases the amount of harmful components included in the exhaust gas. Furthermore, non-uniform output gives rise to engine vibration which in turn causes such disadvantages as increased noise.
In order to overcome the above disadvantages, there have been proposed various apparatuses for individually controlling the fuel to be injected into the respective cylinders of the internal combustion engine according to an individual cylinder control method. Japanese Patent Application Public Disclosure No. 82534/84 discloses an example of an apparatus of this type in which individual cylinder control is carried out on the basis of the result of a detection carried out for every combustion stroke in each cylinder, of the difference between the rotational speed at the time of the combustion of fuel supplied by injection to the multiple cylinder internal combustion engine and the rotational speed at the time when the instantaneous rotational speed of the crankshaft reaches the maximum value as a result of the above-mentioned combustion.
Although there is no problem when this type of method is applied to a 4-cylinder internal combustion engine as shown in the embodiment described in this Public Disclosure, disadvantages such as the following will result if it is applied to, for example, a 6-cylinder internal combustion engine.
In an engine in which combustion arises at a period of less than 180.degree. CA (angle of the crankshaft) such as a 6-cylinder internal combustion engine, the output torque produced during the power stroke of the cylinder under consideration is influenced by the output torque of the cylinders whose power strokes are started at the end portion of the power stroke of the cylinder under consideration and/or terminated at the beginning portion thereof. Accordingly, it is impossible to accurately detect the output of a desired specific cylinder with the method according to the prior art. As a result, when individual cylinder control is carried out in a multi-cylinder internal combustion engine in which combustion occurs at a period of less than 180.degree. CA according to the conventional method, the detection data is inaccurate, creating disadvantages such as an increase in the vibration produced by the internal combustion engine.